As a technique for achieving augmented reality using image recognition technology, a technique using markers is known. However, there is a problem that mechanical-looking markers ruin designs. To solve this problem, there is known a technique in which no marker is used and a target object is identified using a local feature value robust against changes in the state of the target object (rotation of the target object or a change in distance).
However, in the conventional art, there is a problem that recognition accuracy significantly decreases when a shadow or shininess occurs on a target object due to the influence of illumination, etc.